What published RPG do you wish you were playing right now?
I am going under the assumption the question means "playing" as opposed to being the DM (as I usually DM). So with that caveat...Torg Eternity.
I loved the game when it first came out in 1990. My official favorite game system is Masterbook. I bought into the Kickstarter for Torg:Eternity and have thus been able to read the rules in pdf that just came out. It looks like a solid system that definitely captures the setting while retaining much of the rule set I liked. Fortunately, there is a game being started up this Saturday so I will be able to try it out as a player!
That being said I would actually like to be playing my Legion of Stars homebrew which is not published yet, but at least I get to run it every other week.